Field of the Invention
The present invention relates to an information acquisition apparatus that can acquire object information based on a signal originated from an acoustic wave.
Description of the Related Art
As a technique capable of acquiring internal information about a living organism or any other object by receiving an acoustic wave, an information acquisition apparatus, such as a photoacoustic imaging apparatus or an ultrasonic wave echo imaging apparatus, has been proposed.
As discussed in Minghua Xu and Lihong V. Wang, “Universal back-projection algorithm for photoacoustic computed tomography”, PHYSICAL REVIEW E 71, 016706 (2005), there is a conventionally known time domain reverse projection method, which is generally referred to as “Universal Back-Projection.” As discussed in Minghua Xu and Lihong V. Wang, “Universal back-projection algorithm for photoacoustic computed tomography”, PHYSICAL REVIEW E 71, 016706 (2005), it is conventionally known to perform reconstruction by using a single sound speed under an assumption that a measurement target is a uniform medium.
However, in a case where an acoustic wave generated from an object (i.e., a measurement target) propagates a medium that is different from the object in sound speed, it is difficult to accurately acquire the object information according to the method discussed in Minghua Xu and Lihong V. Wang, “Universal back-projection algorithm for photoacoustic computed tomography”, PHYSICAL REVIEW E 71, 016706 (2005), because a significant difference occurs in propagation time when the medium is different from the object in sound speed.